PURPOSE: To improve scratching resistance by incorporating the compd. obtd. by bringing the reaction product of epoxide and polyethylene imine further into reaction with the polymer of 12-hydroxystearic acid and a radiation polymerizable compd.

CONSTITUTION: This compsn. contains (1) the compd. obtd. by bringing the reaction product of the epoxide expressed by formula I and the polyethylene imine further into reaction with the polymer of the 12-hydroxystearic acid and a radiation polymerizable compd. and (2) the radiation polymerizable compd. in a 5:95 to 25:70 range by weight. A hard coat layer having high hardness and ≤1010Ω/sequare surface resistance value can be provided on a plastic substrate for optical disks according to such constitution. The optical disk which overcomes the weak points of the optical disk formed by using the conventional plastic substrate and is excellent in both of scratching resistance value and antistatic function is provided.